<!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <bindings xmlns="http://www.mozilla.org/xbl"
              xmlns:html="http://www.w3.org/1999/xhtml">
      <binding id="x">
        <content>
          <html:span class="a"></html:span>
          <html:span class="b">This should be green</html:span>
          <children/>
        </content>
      </binding>
    </bindings>
    <style>
      #foo { -moz-binding: url("#x"); }
      .a + .b { color: green; }
    </style>
  </head>
  <body>
    <span id="foo"></span>
  </body>
</html>
